1. Field of the Invention
The present disclosure generally relates to an optical input apparatus.
2. Description of the Related Art
Generally, portable electronic devices include portable terminals, MP3 players, Portable Multimedia Players (PMPs), and electronic books, and refer to devices by which users can access various contents while carrying the portable electronic devices.
The portable electronic devices are frequently used while users are mobile due to their portability and various functions associated with the devices. The designs of the portable electronic devices are diversified according to the present day demands and the needs of consumers. Accordingly, portable terminals equipped with various functions, such as bar type smart phones and tablet PCs, are increasingly being used today.
Specifically, as notebook or multimedia functions are included in a bartype portable terminal, various contents such as financial services, game/multimedia services, and wireless Internet services, including voice communications, can be enjoyed using the same portable terminal. In the case of the bar-type portable terminal, a unit for inputting data and a data output unit for displaying an image are embodied as one large-sized display panel on a front surface of the portable terminal.
Touch inputs are widely used in display panels. However, new types of inputs are increasingly being utilized. For example, an input unit using light, such as an optical mouse, has been proposed. An input unit using a light source according to the related art is illustrated in FIGS. 1, 2, 3A, and 3B. FIGS. 1 and 2 are views illustrating an optical pen according to the related art. Referring to FIGS. 1 and 2, the optical pen 10 includes a pen body 11, a pen tip 12, a light source 13, and an image sensor 14. The pen tip 12 protrudes from a front surface of a distal end of the optical pen 10. The light source 13 emits light towards a screen of a display apparatus 20 that is spaced apart from the pen tip 12. The light emitted from the light source 13 is reflected by the screen of the display apparatus 20, and is received by the image sensor 14 of the optical pen 10. Then, a pattern P (FIG. 3B) of the display apparatus 20 is received by the image sensor 14. A controller 15 calculates a change of a location of the optical pen 10 as a function of the pattern P received by the image sensor 14 to output a picture or a letter. FIGS. 3A and 3B are views illustrating a reflective pattern P and an image pattern P received by the image sensor 14. Referring to FIGS. 3A and 3B, in the case of the optical pen 10, deviations are detected in the brightness of light detected by the image sensor 14 according to an inclination angle of the optical pen 10. In an extreme case, the image pattern P detected by the image sensor 14 becomes so dark that errors may be frequently generated when a location of the pattern is determined (it can be seen that the pattern on the right of FIG. 3B is darker than the pattern on the left of FIG. 3B). A locally saturated area D in which light is concentrated in the image pattern P detected by the image sensor 14 is generated. That is, when a user uses the optical pen 10, the optical pen 10 is inclined with respect to a screen of the display apparatus 20. Accordingly, if the body 11 is inclined in a light emitting direction of the light source 13, for example, to the left of the pen tip 12 unlike the case in which the body 11 contacts the screen perpendicularly, light is intensively saturated in a right portion of the screen so that the brightness of the screen is higher or a locally saturated area D, in which light is saturated is generated. That is, the brightness of light is extremely high in the light emitting direction of the light source 13, and thus a locally saturated area is generated. Accordingly, if a local saturation is generated, the image sensor 14 cannot recognize the pattern P, and fails to recognize a point location or a movement of the pen tip 12, decreasing reliability according to a pointing direction of the optical pen 10.
Further, when the light emitted from the light source 13 is reflected by the screen when the optical pen 10 is inclined, it is scattered according to a surface of the screen so that the brightness of an image decreases and the brightness of the pattern detected by the image sensor also decreases, making it possible to recognize the pattern.
In addition, the light emitted from one light source 13 requires a high power consumption to realize a bright image with a short exposure time. Thus, a battery may be exhausted in a short time by a power source provided in the light source 13 or one light source 13 will fail to provide a brighter image.